The invention relates to a method for heating a liquid product flowing through a conduit by means of a medium, wherein the product successively is conveyed under overpressure to a heating apparatus, subsequently passes through an insulated dwelling stretch and then, through an adjustable throttle valve, arrives in an expansion vessel from which the treated product is discharged. Such a method is known per se and is widely practised in the dairy and food products industry. Thereby two systems can be discerned, to wit an indirect heating system while utilizing a heat exchanger and a direct heating system by means of an injection of steam into the product.
A drawback of the known methods is, however, that the capacity cannot or hardly be altered without the treating temperature in the dwelling stretch thereby exhibiting inadmissible fluctuations. The cause of this is the fact that the actual process proceeds very rapidly and is also dependent on the ratio of product mass flow to heating medium mass flow and on the pressure at which the heating takes place. Moreover, there is the additional phenomenon of dynamic instability of the process, i.e. as soon as the ratio of product mass flow to medium mass flow alters, this ratio, and with it the heating temperature, instead of being reinstated, still further alters.